181P Efficacy of eribulin mesylate in HER2-low metastatic breast cancer (MBC): Results from a pooled analysis of two phase III studies

Abstract

Breast cancer (BC) with low-level HER2 expression (HER2-low) is defined by an immunohistochemistry (IHC) score of 1+ or 2+ without HER2 gene amplification or excess gene copy number, as measured by in situ hybridization (ISH). This represents approximately half of patients (pts) with BC overall (estimated 55% in hormone-receptor-positive BC and 38% in triple-negative BC; Scott ASCO 2021). Studies have suggested that HER2-low BC may respond differently to treatment than BC with no HER2 expression (HER2-0).